Since bottles made of synthetic resin which are represented by PET bottles are inexpensive in terms of costs, in addition to being lightweight and easy to handle, and assuming an appearance which is in no way inferior to glass containers while ensuring transparency, the bottles are mainly used as beverage containers.
Meanwhile, this kind of bottle has the disadvantage that because the thickness of the body is thin, when the inside of the bottle is brought into a pressure-reduced state, the body is deformed in irregular shapes, such as an elliptical or a triangular shape. In a case where the body has been deformed in this way, there is a problem in that not only is the aesthetic appearance impaired, but the operability is poor. Particularly in a case where the bottle is made lightweight by reducing its thickness, this problem becomes more conspicuous.
Thus, in order to suppress irregular deformation of the body caused when the internal pressure of the container drops (pressure is reduced), a bottle in which the body is provided with a pressure-reduction absorption panel is developed. However, since this type of bottle is inevitably restricted by the pressure-reduction absorption panel at the time of design, freedom of design is not possible, and problems are left unsolved in terms of design performance.
Apart from this, an unpanelled bottle which can suppress irregular deformation of a body at the time of pressure reduction without providing the body with a pressure-reduction absorption panel has recently been provided (see Patent Document 1 and Patent Document 2).
This bottle is a bottle in which an annular groove is formed in the outer peripheral surface of the body, and the body is capable of being contracted and deformed in the axial direction (longitudinal direction) with the annular groove as a center. That is, this bottle is designed so that a pressure change at the time of pressure reduction can be absorbed by contracting and deforming the body in the axial direction.
Additionally, as the compressively deformable bottle, for example, there is a heat-filled bottle (for example, refer to Patent Document 3) including a mouth, a cylindrical neck tube connected via a neck ring provided in the mouth, a shoulder which is enlarged in diameter integrally from the neck tube, a body connected to the shoulder, and a bottom connected to the body via a heel, which are integrally molded. Here, an annular recess which splits the body into an upper portion and a lower portion is formed by recessing a portion of the body radially inward along the circumference of an axis, and the deformation accompanying a pressure reduction effect after cooling is absorbed by making an upper surface of the annular recess connected to the upper portion foldable toward a lower surface of the annular recess connected to the lower portion.